Method of making chromium steel and chromium iron



Patented July 15, I924.

NAPOLEON rn'rmor,

' ism-s33 on NEW YoLaK, N. Y.

METHOD OI MAKING CHROMIUM STEEL AND CHROMIULI IRON.

No Drawing. i

To all whom it may concern:

Be it known that I, N APOLEON PETINOT, a citizen of the United States of America, and a resident of the city, county, and State of New York, have invented new and useful Methods of Making Chromium Steel and Chromium Iron, of which the following is a full, clear, and exact description.

This invention relates to anew method of- -making additions of chromium to steel or have a carbon content of 8% orless) is as p10 a ferrovchromium-sllicon allo having a bath of molten steel. Then by suitable treatment the bath is adjusted until it has the desired composition, as regards the usual components of ordinary steels such as iron,

. carbon, silicon, maganese, sulphur, and phosphorus. Then, as the last step, towards the end of the heat and before the furnace is tapped, a-'ferro-chromiu1n alloyv is added in such quantity that the desired content of chromium will be found in the finished steel. Frequently it is found necessary at this laststage to add some silicon to the steel in order that it may contain the amount of that metal that is called for in the specifications for the finished product. If silicon is thus employed, its introduction. is made in the ladle when the furnace is tapped.

One of the most serious difiiculties encountered in the manufacture of chromium steels by this method is that a large amount of chromium is lostby oxidation when the ferro-chromium is added to the bath. This diliiculty makes the accurate adjustment of the chromium content a very difiicult and delicate thing. Moreover, this method is expensive since the oxidized chromium is slagged' OH, and chromium is an expensive element.

A typical analysis of -ferro-chromium, such as is used in makin chromium steels, (I refer particularly to those grades which follows:

. Cr. 64.0%; Fe. 28.5% C. 5.5%; Si. 0.4%;

A1. O. 5%; Mn. 0.15%; Ga. 0.25%; S. 0.04%

1 Application filed m 13',

1922. Serial No. 575,804.

It will be observed that the carbon colitent .of this ferro-chromium amounts to 5.5%.

When such an alloy is added to the steel certain extent, prevents the loss of chromium by oxidation, so that the higher the percentage of carbon present, the less wil be the chromium loss.

This, however, is not a satisfactory method of taking care of the chromium losses due to oxidation, since some of the carbon is apt to be taken up by the steel-thereby disturbing the desired carbon content of the finished product. On the other hand, the lower the carbon content is in the added ferro-chromium the more costly the ferrochromium is and hence the more serious economically, is the loss of chromium by oxidation.

It should also be noted that the typical commercial grades of ferro-chromium are alwavs low in silicon; the silicon content usually running as low as 0.4 to 1.5 per cent.

The invention described herein improves the methods heretofore used in that the loss of chromiumby oxidation is substantially eliminated.

In carrying out my invention, I prepare -my steel or iron in the furnace (for example,

an open hearth furnace) in. the usual way. Just before tapping the furnace I add a quantity of my ferro-chromium-silicon alloy,

which-usually and preferably containsfrom two per cent to ten per cent of silicon. The amount of such alloy to be added depends upon the amount of chromium which 15 desired in the finished product.

Usually. the ferro-chromium-silicon alloy used in carrying out my process has a silicon content of from two to ten per cent, that content being suficient to protect the chromium from oxidation without affecting the silicon content of the bath.

My invention, however, is not confined to the addition of a ferro-chromium-silicon alloy of such low silicon content as that last abovedescribed. I have found that an alloy of such character may be advantageously used which has as high a silicon content as fifty per cent when it is desired to produce a chromium steel of hi h silicon content.

In carryingout my invention, I mayemsue ,a' silicon content that the si 'con*-not-1*10+ onlyrotects the chromium from oxidation,

of silicon in the bath. Obviously some modifications of my mbath thereby increasing the absolute quantity vention as herein described may be made without departing-from the s irit thereof, and I do not wish to be limite to the exact method in all of its details as herein described.

Having thus described my invention, what I claim 1s: f

1.. A method of making chromium steel or chromium iron comprising the addition to the molten iron bath of a ferro-chromiumsilicon alloy containing suflicient silicon to protect the chromium'from oxidation.

2. A method of making chromium steel or chromium iron com rising the addition to amount.

3. A method for making chromium steel or chromium iron comprising the addition to themolten iron bath of a ferro-chromiumsilicon alloy containing suflicient siliconto not only protect the chromium from oxidation but also to .bring the silicon content of the finished product 11 to at leasttwo and one-half per cent of si 'con.

4. A method for making chromium'steel or chromium iron comprisin the addition to the molten iron bath of a erro-chromiumsilicon 'alloy containing sufiicient silicon to not only protect the chromium from oxidation but also to bring the silicon content of thefinished product up to not more than fifty per cent of silicon.

5. A method for making chromium steel or chromium iron comprising the addition to the molten iron bath of a ferro-chromiumsilicon alloy containing suflicient silicon to not only protect the chromium from oxidation but also to bring the silicon content of the finished roduct up to not less than two and one-hali per cent and not more than fifty per cent of silicon. v

In witness whereof, I have hereunto signed my name.

' NAPOLEON PETINOT. 

